IJCS | Volume 31, Nº6, November / December 2018

589 Figure 2 - Electron photomicrographs of atrial cardiomyocytes of infected groups. In (A), the untrained infected group (UI) presents a large amount of collagen fibers in the interstitium. Some nuclear envelopes have an irregular thickness and numerous invaginations, while others have a rectilinear thickness and precise contours with the cytoplasm. The nuclear chromatin shows heterogeneous electron density with intensely dense regions near the nuclear envelope, mitochondria without evident ridges, concentration of granules, mostly small, on the periphery of myocytes, and preserved structure of myofibrils and Z lines. In (B), the trained infected group (TI) presents irregular interstitium with plenty of collagen fibers. The cytoplasmic membrane in most myocytes has an irregular contour with numerous invaginations, and the cytoplasm has numerous scattered or grouped mitochondria and rare suggestion of degeneration. The nuclear chromatin is heterogeneous with electron-dense regions disseminated throughout the nucleus, and along the nuclear envelope. There is a predominance of small atrial granules scattered in the cytoplasm, in the nuclear poles, and the surface of the cytoplasmic membrane. Both myofibril and Z line are thickened. Table 2 - Apparatus of atrial cardiomyocytes in mice in the untrained control (UC), trained control (TC), untrained infected (UI), and trained infected (TI) groups Parameters /group UC TC UI TI Vv [gr] (%) 4.43 ± 0.36 4.02 ± 0.66 3.18 ± 0.19* 6.16 ± 0.5 + Vv [mit] (%) 16.5 ± 1.05 26.91 ± 4.3* 15.56 ± 1.16* # 23.68 ± 2.08* + Vv [miof] (%) 56.32 ± 1.67 46.01 ± 4.01* 55.43 ± 1.60 # 44.45 ± 2.02* #+ Vv [golgi] (%) 4.74 ± 0.30 4.94 ± 0.60 7.15 ± 0.39* # 5.48 ± 0.38 + Vv[others] % 7.23 ± 1.63 11.82 ± 4.0 8.15 ± 1.6 9.64 ± 1.66 Vv [int] (%) 10.28 ± 1.17 7.55 ± 1.97 10.6 ± 0.94 9.02 ± 1.06 Values are presented as mean ± standard error of mean. *p < 0.05 versus UC; #p < 0.05 versus TC and +p < 0.05 versus UI. Abbreviations: Vv[gr]: volumetric density of granules; Vv[mit]: mitochondria; Vv[myofib]: myofibrils; Vv[golgi]: Golgi complex; Vv[int]: interstitium; Vv[others]: others. Ferraboli et al. Effect of mild aerobic exercise in Chagas’disease Int J Cardiovasc Sci. 2018;31(6)585-593 Original Article heart disease, and found a disproportionate elevation of ANP after physical exercise in ischemia. Zhu et al. 32 analyzed postmortem pericardial ANP and showed that ANP levels correlated negatively with pericardial cardiac troponin levels, while Tanaka et al. 33 found that RA cardiomyocytes are prevalent in the production of ANP. Many studies have been performed analyzing the stimulation of ANP secretion by physical exercise. 34-38